CWE-682: Incorrect Calculation

How it's found

Incorrect Calculation is a broad weakness category rather than one exact bug. Testers narrow it down through manual code review and architecture review to identify which of its more specific child weaknesses actually appears in a given target, then confirm each one individually.

When product performs a security-critical calculation incorrectly, it might lead to incorrect resource allocations, incorrect privilege assignments, or failed comparisons among other things. Many of the direct results of an incorrect calculation can lead to even larger problems such as failed protection mechanisms or even arbitrary code execution.

Consequences

• DoS: Crash, Exit, or Restart: If the incorrect calculation causes the program to move into an unexpected state, it may lead to a crash or impairment of service.
• DoS: Crash, Exit, or Restart, DoS: Resource Consumption (Other), Execute Unauthorized Code or Commands: If the incorrect calculation is used in the context of resource allocation, it could lead to an out-of-bounds operation (CWE-119) leading to a crash or even arbitrary code execution. Alternatively, it may result in an integer overflow (CWE-190) and / or a resource consumption problem (CWE-400).
• Gain Privileges or Assume Identity: In the context of privilege or permissions assignment, an incorrect calculation can provide an attacker with access to sensitive resources.
• Bypass Protection Mechanism: If the incorrect calculation leads to an insufficient comparison (CWE-697), it may compromise a protection mechanism such as a validation routine and allow an attacker to bypass the security-critical code.

Mitigations

• Implementation: Understand your programming language's underlying representation and how it interacts with numeric calculation. Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions, truncation, conversion and casting between types, "not-a-number" calculations, and how your language handles numbers that are too large or too small for its underlying representation.
• Implementation: Perform input validation on any numeric input by ensuring that it is within the expected range. Enforce that the input meets both the minimum and maximum requirements for the expected range.
• Implementation: Use the appropriate type for the desired action. For example, in C/C++, only use unsigned types for values that could never be negative, such as height, width, or other numbers related to quantity.
• Architecture and Design: Use languages, libraries, or frameworks that make it easier to handle numbers without unexpected consequences. Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++).
• Architecture and Design: Use languages, libraries, or frameworks that make it easier to handle numbers without unexpected consequences. Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++).
• Implementation: Examine compiler warnings closely and eliminate problems with potential security implications, such as signed / unsigned mismatch in memory operations, or use of uninitialized variables. Even if the weakness is rarely exploitable, a single failure may lead to the compromise of the entire system.

Where this fits in a TurboPentest engagement

This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.

Frequently asked questions